Method and device for rising casting with a sliding closure that is mounted on the mould frame

ABSTRACT

A method for uphill casting/low-pressure casting, especially of light metal alloys, with a casting furnace lying below a casting table, having a riser pipe and a mouth opening of the riser pipe and having a mould with an underlying pouring-in opening and having a slide valve closure, forming a flow-through channel which for casting takes on a substantially straight, longitudinal course, wherein for shut-off in the slide valve closure, two opening sections of the flow-through channel directly adjacent one to the other are displaced with respect to one another transversely to the longitudinal course of the flow-through channel directly after casting with still liquid melt in the pouring-in opening, so that an overlying opening section remains in open communication with the pouring-in opening free from undercut and an underlying opening section remains in open communication with the mouth opening of the riser pipe, wherein the opening sections are completely offset with respect to each other.

[0001] The invention relates to a method and an apparatus for uphillcasting/low-pressure casting, especially of light metal alloys, with acasting furnace lying below a casting table, having a riser pipe and amouth opening of the riser pipe and having a mould with an underlyingpouring-in opening and having a slide valve closure for the pouring-inopening, forming a flow-through channel which for casting takes on asubstantially straight, longitudinal course.

[0002] Compared with gravity casting, uphill casting has the substantialadvantage of a smooth controlled casting process. By this means theentrance of air bubbles and oxidation skin which is associated with anyturbulence of the melt during casting is avoided. When using corepackages as moulds, the separation and entrainment of moulding materialin the gate and in the runner can be avoided which otherwise leads to adeterioration in the quality of the castings.

[0003] A disadvantage with uphill casting is that in general it isnecessary to wait for the solidification process of up to 15 minutesduration before the mould just filled can be removed and the next mouldcan be brought over the casting furnace. In order to rectify thisdisadvantage, it has already been proposed that moulds should be closeddirectly after the low-pressure casting in the pouring-in opening andremoved immediately from the riser pipe.

[0004] It is known from CH 415 972 that moulds for low-pressure castingcan be provided with an underlying shut-off valve and a feeder headpositioned thereover, below the mould cavity. The shut-off valveconsists of a slider plate lying inside a pouring-in channel with aflow-through opening which is displaced transversely with respect to thepouring-in channel. The feeder head has a volume-displacing sliderpiston. Although the feeder head is heatable, after closure of theshut-off valve there may be some solidification of the melt in theflow-through opening of the slider plate, which requires separateremoval of the plug there formed before the next casting process.

[0005] The object of the following invention is to further improve amethod and an apparatus of said type.

[0006] The solution lies in a method for uphill casting/low-pressurecasting in which for shut-off in the slide valve closure, two openingsections of the flow-through channel directly adjacent one to the otherare displaced with respect to one another transversely to thelongitudinal course of the flow-through channel directly after castingwith still liquid melt in the pouring-in opening, so that an overlyingopening section remains in open communication with the pouring-inopening free from undercut and an underlying opening section remains inopen communication with the mouth opening of the riser pipe, wherein theopening sections are completely offset with respect to each other. Acorresponding apparatus according to the invention is characterised inthat the slide valve closure is placed on the casting table andcomprises two mutually displaceable plates, each having a flow-throughopening, wherein the plates can brought into overlap with theirflow-through openings for casting and the plates are displaceabletowards each other for shut-off so that the flow-through opening in theupper plate is in open communication with the pouring-in opening freefrom undercut and the flow-through opening in the lower plate is in opencommunication with the mouth opening of the riser pipe, while thesections of the flow-through opening are completely offset with respectto each other.

[0007] With the method according to the invention and the apparatusaccording to the invention, a method is provided especially suitable forsmall castings in which it is not necessary to separate the riser pipefrom the slide valve closure during successive casting processes so thatany air access to the melt level in the riser pipe can be largelyexcluded. This particularly applies if, after shut-off, the melt in theriser pipe is only lowered so far that at least the lower longitudinalsection of the flow-through channel is emptied of melt, to avoid anysticking of melt to the upper slide plate. Here it can especially beprovided that after shut-off, the melt in the riser pipe is only loweredto slightly below the mouth opening of the riser pipe and that duringlowering of the melt, the riser pipe is acted upon by protective gas atthe mouth opening.

[0008] In a preferred embodiment, the process sequence is distinguishedby the fact that the mould itself as an entity is displaced togetherwith the upper longitudinal section of the flow-through channel of theslider unit. In order to accelerate the process sequence, it is herebyprovided that the melt should be actively cooled inside the pouring-inopening and if necessary, also inside the upper longitudinal section ofthe flow-through channel at the latest after shut-off, i.e., thedisplacement of the longitudinal sections of the flow-through channeltowards to one another. In this case, a mould is then removed from theslide valve closure immediately after solidification of the melt in theupper longitudinal section of the flow-through channel and in thepouring-in opening of the mould. It is thus not necessary to wait forsolidification of the entire casting. In order to avoid shrinkagecaritation during the complete solidification, either a subsequentactive pressure application from above or a rotation of the mouldthrough 180° after lifting is to be proposed. The effortless removal ofthe mould results from the undercut-free configuration of the uppersection of the flow-through channel in which an easily demouldable plugforms on the casting. This is achieved by the flow-through opening inthe upper plate and if necessary, jointly with this the pouring-inopening of the mould, expanding continuously upwards, especially havingan upwardly expanding conicity.

[0009] The apparatus according to the invention is especiallyconstructed such that the plates are held in a cassette fixed to thecasting table and the upper plate is held in a holder displaceable inthe cassette, on which the mould can be placed. This holder canespecially be inserted in a sliding carriage guided in the cassette onwhich it is supported in a spring fashion.

[0010] A suitable mould can have a lower cylindrical connecting piecewhich forms the pouring-in opening and which fits into aconnecting-piece insert or a connecting-piece receptacle in the holderfor the upper plate which is aligned towards the flow-through opening inthe upper plate. Here especially the front face of the cylindricalconnecting piece of the mould can be positioned flush onto the upperplate and if the mould's own weight is too low, can be braced againstthis to produce an effective seal. In order to accelerate the sequenceof the casting processes as specified above, there are provided ascooling devices a coolant ring at the connecting-piece insert or theconnecting-piece receptacle in the holder of the upper plate and acooling chamber below or in the lower plate. The coolant feed pipe tothe coolant ring must be elastic in this case in order to be able toequalize the movements of the sliding carriage or the holder. Theactuating device for the sliding carriage can be arranged directly onthe cassette. The mould can be designed as a permanent mould or consistentirely of mould material. The connection between the riser pipe andthe slider unit can be such that the riser pipe passes through thecasting table in an opening and abuts with a contact plate directlyagainst the stationary lower slide plate. However, it is also possiblethat there is inserted securely in the casting table a sprue bushingwhich lines the opening in the casting table and is clamped against thelower slide plate in a sealing fashion and that the riser pipe abutswith a contact plate against the lower edge of this sprue bushing. It ispreferably provided that the flow-through opening in the lower plateand, if necessary, jointly with this, the parts forming the flow-throughchannel adjacent thereto in the downward direction as far as the mouthof the riser pipe, jointly expand continuously downwards, especiallyhaving a downward-expanding conicity so that when the melt level in theriser pipe is allowed to drop, no melt residue is caught in theflow-through channel.

[0011] The riser pipe can be axially elastically and angularly moveablyjoined to the casting furnace via a metal bellows connection while thecasting furnace is held such that it is moveable in height to allowdocking of the riser pipe at the casting table and separation of theriser pipe from the casting table. With the same type of axial elasticand angular moveable connection between the casting furnace and theriser pipe by means of a metal bellows, the casting table can also bemoveable in height in kinematic permutation in order to accomplish saiddocking and separation between the riser pipe and the casting table.

[0012] Insofar as uphill casting/low-pressure casting according to theinvention is discussed heretofor, this initially relates to methods andapparatus wherein a controllable gas pressure is applied to the meltlevel in the sealed furnace, which makes the melt in the riser pipe riseor fall. Also included however are other methods and apparatus which cancontrollably convey the melt in the riser pipe, e.g. magnetic pumpingarrangements at the lower end of the riser pipe in the casting furnace.

[0013] The uphill casting/low-pressure casting is hereinbefore relatedto a perpendicular gate of the moulds wherefrom are derived thecorresponding designations upper plate/upper section of the flow-throughopening, lower plate/lower section of the flow-through opening. Thesubject matter of the invention is not departed from, however, if mouldshaving horizontal gates are used, wherein the term “upper” is logicallyto be replaced by “mould-side” and the term “lower” is logically to bereplaced by “riser pipe side” with a horizontally aligned flow-throughdirection but otherwise unchanged geometry and kinematics.

[0014] Details of the apparatus according to the invention are describedin the following with reference to the drawings, wherein

[0015]FIG. 1 shows an apparatus according to the invention in a firstposition during the casting process;

[0016]FIG. 2 shows the apparatus according to the invention as in FIG. 1in a second position during the solidification process in the sprue.

[0017] The two figures are first described jointly. A slider unit 13 isscrewed onto a casting table 11 having a flow-through opening 12. In theflow-through opening 12 of the casting table 11 is inserted a spruebushing 15 which at the same time forms a connection for the riser pipeof a casting furnace not shown. Inside the sprue bushing 15 there isprovided an undercut-free opening 16 down to the riser pipe. The sliderunit 13 comprises a cassette 17 which is screwed directly onto thecasting table 11. For its part this cassette 17 has a lower opening 18which is flush with said opening 16. In the opening 18 there is inserteda sealing ring 14 which abuts against the sprue bushing 15 in a sealingfashion. In the cassette 17 there is inserted a lower slide plate 19.The lower slide plate 19 is held via a thrust piece by a screw 21screwed into the cassette 17. Inside the cassette 17 a holder 22 is heldhorizontally displaceably. In the holder there is inserted an upperslide plate 23 which has an upper flow-through opening 24 of the sliderunit. The holder 22 is arranged at a sliding carriage 25 which is heldby guide rails 26 in the cassette 17. Inserted in the sliding carriage25 are compression spring domes 30, 31 whose pressure cylinders 32, 33press the holder 22 downwards so that the slide plates 19, 23 abut ontoeach other with pre-stressing and fit in the cassette 17. Attached tothe cassette 17 is an adjusting cylinder unit 28 which acts via a rod 29on the sliding carriage 25 so that the holder 22 can be displacedhorizontally in the cassette 17.

[0018] The lower slide plate 19 has a lower flow-through opening 20, theupper slide plate 23 has an upper flow-through opening 24. In coaxialassignment to the upper flow-through opening 24 the holder 22 has aconnecting-piece projection 34 and the sliding carriage 25 has aconnecting-piece receptacle 35. Also inserted in the connecting-pieceprojection 34 is a cooling ring 36 shown in enlarged detail, which canbe supplied with cooling air via a compressed-air line 37. The coolingring 36 has inwardly directed air outlet openings 38. In the lower slideplate 19 there is constructed a cooling chamber 39 which is suppliedwith cooling air via another compressed air line 40. Inserted in theconnecting-piece projection 34 and the connecting-piece receptacle 35 isa mould 41 having a downward-pointing sprue connecting piece 42 whichsits on the upper slide plate 23. The mould 41 is sealed by a lid 43.The sprue channel 44 of the mould 41 is flush with the upperflow-through opening 24 and jointly with this, is undercut-free in theupward direction, and especially is constructed as conically opening.The mould 41 can be a permanent mould or a sand mould or a core package.

[0019]FIG. 1 shows the position of the slider unit 13 for casting. Thesliding carriage 25 with the holder 22 is pushed by means of theadjusting cylinder 28 into its right-hand position inside the cassette17. In this case, the opening 16 in the sprue bushing 15, theflow-through opening 20 in the lower plate 19, the flow-through opening24 in the upper plate 23 and the sprue channel 44 of the mould 41 areflush with one another. An arrow indicates how melt can be fed from ariser pipe to the opening 16 in the sprue bushing 15, to rise via thelower flow-through opening 20 and the upper flow-through opening 24 inthe mould 41 until th's is filled. Only at this point in time is it morelogical to begin supplying cooling air to the cooling ring 36.

[0020]FIG. 2 shows how the sliding carriage 25 with the holder 21 isdisplaced by means of the adjusting cylinder 28 into the left-handposition inside the cassette 17 after completion of the casting process,wherein the upper flow-through opening 24 is sheared towards the lowerflow-through opening 20 so that there is no longer any connection fromthe riser pipe to the mould. Only at this point in time is it morelogical to supply cooling air to the cooling chamber 39 to make the meltin the now overlying sprue channel 44 solidify. After rapidsolidification of the melt in the sprue channel 44, which can beaccelerated by cooling the sprue connecting piece 42, the mould 41 canbe lifted, wherein the plug in the upper flow-through opening 24 caneasily be demoulded upwards on account of its upwardly conically openingundercut-free shape. From the opening 16 in the bushing 15 and theflow-through opening 20 in the lower plate 19, the melt is dropped backin the riser pipe as a result of pressure reduction in said pipe, asindicated by an arrow. In this case, the flow-through opening at leastin the area of the sprue bushing 15, opens conically downwards with atotally undercut-free continuous course. After removal of the mould, anew mould is put in position and the apparatus is returned to theposition as in FIG. 1 in which a further casting process can begin.

[0021] List of Reference Symbols

[0022]11 Casting table

[0023]13 Flow-through opening (11)

[0024]13 Slider unit

[0025]14 Seal

[0026]15 Sprue bushing

[0027]16 Opening (15)

[0028]17 Cassette

[0029]18 Opening (17)

[0030]19 Lower plate

[0031]20 Lower flow-through opening (19)

[0032]21 Screw

[0033]22 Holder

[0034]23 Upper plate

[0035]24 Upper flow-through opening (23)

[0036]25 Sliding carriage

[0037]26 Guide

[0038]27 Connecting-piece projection

[0039]28 Adjusting cylinder

[0040]29 Rod

[0041]30 Spring dome

[0042]31 Spring dome

[0043]32 Pressure cylinder

[0044]33 Pressure cylinder

[0045]34 Connecting-piece projection

[0046]35 Connecting-piece receptacle

[0047]36 Cooling ring

[0048]37 Compressed-air line

[0049]38 Air outlet opening

[0050]39 Cooling chamber

[0051]40 Compressed-air line

[0052]41 Mould

[0053]42 Sprue connecting piece

[0054]43 Lid

[0055]44 Sprue channel/pouring-in opening

1-21. (Cancelled).
 22. The method of claim 39, further comprisinglowering the liquid melt in the riser pipe after the slide valve closureis shut-off until at least the underlying opening section of theflow-through channel is emptied of liquid melt.
 23. The method of claim22, further comprising lowering the liquid melt in the riser pipe as faras slightly below the mouth opening of the riser pipe after the slidevalve closure is shut off.
 24. The method of claim 22, furthercomprising introducing a protective gas at the mouth opening of theriser pipe during the lowering of the liquid melt.
 25. The method ofclaim 39, further comprising displacing the overlying opening section ofthe flow-through channel jointly with the pouring-in hole of the mouldwith respect to the underlying opening section of the flow-throughchannel, said underlying opening section being held in a fixed positionat the mouth opening of the riser pipe.
 26. The method of claim 25,further comprising displacing the mould together with the overlyingopening section of the flow-through channel.
 27. The method of claim 39,further comprising actively cooling the liquid melt inside thepouring-in hole of the mould at the latest from the time the two openingsections of the flow-through channel are displaced with respect to eachother.
 28. The method of claim 39, further comprising removing the mouldfrom the slide valve closure immediately after solidification of theliquid melt in the overlying opening section of the flow-through channeland in the pouring-in hole of the mould.
 29. (Cancelled).
 30. Theapparatus of claim 41, wherein the plates are held in a cassette securedto the casting table, and wherein the upper plate is held in thedisplaceable holder in the cassette on which the mould is placed. 31.The apparatus of claim 41, wherein the mould comprises a lowercylindrical sprue connecting piece, said sprue connecting piece formingthe pouring-in hole which fits into a connecting-piece projection of thedisplaceable holder, said connecting piece projection being alignedtowards the flow-through opening in the upper plate.
 32. The apparatusof claim 31, wherein the front face of the cylindrical sprue connectingpiece is placed on the upper plate.
 33. The apparatus of claim 41,further comprising a coolant chamber below or inside the lower plate,said coolant chamber being connected to a coolant line.
 34. Theapparatus of claim 41, further comprising an actuating device for theholder, wherein said actuating device is arranged on the cassette. 35.The apparatus of claim 41, further comprising spring means acting on theholder, said spring means being supported in the cassette, and holdingthe upper plate and the lower plate braced against each other.
 36. Theapparatus of claim 41, wherein the riser pipe is suspended elasticallyflexibly in the casting furnace being adjustable in height with respectto the casting table.
 37. The apparatus of claim 41, wherein theflow-through opening in the upper plate and the pouring-in holecontinuously expand upwards, said flow-through opening and saidpouring-in hole exhibiting an upwardly expanding conicity.
 38. Theapparatus of claim 41, wherein the flow-through opening in the lowerplate and parts adjacent thereto in the downward direction as far as themouth of the riser pipe, forming the flow-through channel, continuouslyexpand downwards, exhibiting a downwardly expanding conicity.
 39. Amethod for uphill/low pressure casting a liquid melt in a device whichcomprises a casting furnace lying below a casting table, the castingfurnace having a riser pipe with a mouth opening, a mould having anunderlying pouring-in hole, and a slide valve closure forming aflow-through channel comprising a substantially straight, longitudinalcourse during casting of the liquid melt, the flow-through channel beingformed from an overlying opening section and an underlying openingsection which are directly adjacent to one another, said methodcomprising: casting the liquid melt in the pouring-in hole of the mould;shutting off the slide valve closure; displaying the overlying andunderlying opening sections of the flow through channel with respect toone another and transversely to the longitudinal course of theflow-through channel directly after casting the liquid melt in thepouring-in hole of the mould, so that the overlying opening sectionremains in open communication with the pouring-in hole of the mould andthe underlying opening section remains in open communication with themouth opening of the riser, and the overlying and underlying sectionsare completely offset with respect to one another; and actively coolingthe liquid melt located inside the overlying opening section of theflow-through channel beginning at the latest from the time the twoopening sections of the flow-through channel are displaced with respectto one another.
 40. The method of claim 39, wherein said liquid meltcomprises light metal alloys.
 41. An apparatus for uphill/low-pressurecasting a liquid melt, said apparatus comprising: a casting furnacelying below a casting table, the casting furnace having a riser pipewith a mouth opening; a mould having an underlying pouring-in hole; anda slide valve closure constituting a flow-through channel comprising asubstantially straight, longitudinal course during casting of the liquidmelt, wherein the slide valve closure is located on the casting tableand comprises two plates, an upper plate and a lower plate, said twoplates being mutually displaceable and each having a flow-throughopening, wherein the two plates overlap with their flow-through openingsduring the casting of the liquid melt and are displaceable towards eachother for shut-off so that the flow-through opening in the upper plateis in open communication with the pouring-in hole free from undercut andthe flow-through opening in the lower plate is in open communicationwith the mouth opening of the riser pipe while the flow-through openingsare completely offset with respect to each other, and wherein aconnecting-piece projection of a displaceable holder is surrounded by acoolant ring in the holder, said holder being connected to a coolantline.
 42. The apparatus of claim 41, wherein the liquid melt furthercomprises light metal alloys.
 43. The apparatus of claim 32, wherein thefront face of the cylindrical sprue is braceable against the upperplate.